Vehicle control systems may be used with transportation networks to prevent more than one vehicle from traversing a given route at the same time to help avoid accidents. Further, such control systems may be used to prevent damage to switches or other track components, for example, by preventing a vehicle from traversing over a switch when the switch is not in the proper alignment relative to the vehicle's path. Such control systems may be disposed on-board a vehicle, and configured to stop the vehicle or otherwise prevent the vehicle from traversing an intended path when another vehicle is determined to be on the route, or when a switch or other component is not in a correct alignment. For example, if a train enters a mainline track from a siding when the switch leading to the mainline is not properly aligned, the train may damage the switch, resulting in required time and expense for repair and/or replacement. Further, the entry of a train onto the mainline may result in a collision with another train on the mainline if the position of one or more of the trains is not known.
A control system may include interlocked routes that may form one dimensional rail paths to represent one or more transportation networks. In other words, a train's path may be described as a series of mile posts or other interval markers between a starting and an end point. The path may also include control points such as switches, sidings, stations, or the like where the train may traverse alternate route segments, or switch from one track or route to another. Control systems, such as the Incremental Train Control System (“ITCS”) of GE Transportation, may include a communication-based signal system that identifies vehicle location using global positioning system (GPS) data received onboard a vehicle, such as a train. The control system may need to determine the vehicle's position to enforce speed limits or other regulations or targets as the vehicle traverses the route.
However, the accuracy of GPS data may not be sufficient to identify a particular route or track that the vehicle is on if there are multiple (e.g., parallel) tracks in the area. Thus, a vehicle may have to move to an area where there is only a single track or route before the position of the vehicle may be determined. Thus, the control system may not be allowed to be used until the vehicle is in a single track area, increasing the risk of accident and/or preventing the vehicle from benefiting from the control system.
A need exists for improved determination of location for vehicles in areas having multiple routes or tracks.